Saturday, November 16, 2013

In 2000, a bloom of sea tomato jellyfish in Australia was so enormous —
it stretched for more than 1,000 miles from north to south — that it
was even visible from space.

It was certainly a bloom that Australian
jellyfish researcher Lisa-ann Gershwin won't forget.
While most blooms are not quite that big, Gershwin's survey of research on jellyfish from the last few decades indicate that populations are most likely on the rise, and that this boom is taking place in an ocean that is faced with overfishing,
acid rain, nutrient pollution from fertilizers and climate change,
among other problems.
There have been many reports about jellyfish
numbers increasing in the past few years; some researchers think it is
part of a larger trend, while others say it may be just a numerical
fluke.
Most agree, however, that more data is needed before coming to a
definitive conclusion.

Gershwin, a research scientist with the Commonwealth Scientific and
Industrial Research Organisation who specializes in jellyfish, recently
wrote about her findings in a book called "Stung! On Jellyfish Blooms
and the Future of the Ocean" (University Of Chicago Press, 2013).
The
book, which is aimed at a general audience and is not peer-reviewed,
details dozens of studies that Gershwin read and concludes it's possible
that ocean conditions are ripe for a jellyfish takeover. [Image Gallery: Jellyfish Rule!]

"What we see in the areas that are the most damaged from numerous
different disturbances, we see these jellyfish bloom problems," Gershwin
told LiveScience.
In the Sea of Japan, for example, jellyfish are drifting in from China,
where reports indicate the country is facing massive overfishing and
pollution, as well as coastal construction where jellyfish polyps (or
young) can find a home, Gershwin said.

Some researchers say that overfishing removes other species that
compete for the same food jellyfish eat, such as plankton.
Gershwin
thinks that overfishing, climate change
and a combination of other factors are clearing the way for a jellyfish
takeover. Jellyfish are said to prefer warmer oceans; no direct link
has been found for why acidification would benefit them, according to a
2008 paper in the journal Limnology and Oceanography, but some
researchers say jellyfish increase in abundance in acidic conditions.
"The jellyfish seem to be the ones that are flourishing in this while everything else is suffering," Gershwin said.

The trouble with tracking jellyfish, however, is it's hard to estimate
populations on sight.
Given the creatures are underwater, there are few
records right now — let alone from the past few decades — indicating the
extent of jellyfish populations and how they are changing.
Gershwin
acknowledges that more "good, brilliant, innovative, creative
scientists" are required to find the links between jellyfish population
increases and their causes.

In one 2012 analysis of jellyfish population
reports dating back to the 19th century, researchers publishing in the
journal Proceedings of the National Academy of Sciences unveiled a 20-year cycle in jellyfish abundance.
Another paper published that year in the journal Hydrobiologia,
however, tracked jellyfish increases at the most surveyed "large marine
ecosystem" locations since 1950.

The paucity of data means it is difficult to draw any conclusions about
what is happening, jellyfish researcher Steven Haddock, of Monterey Bay
Aquarium Research Institute in California, told LiveScience.
"It's not to say climate change isn't happening. It's not to say
jellyfish [population increase] is not happening," Haddock said.
"But I
think there are so many causes that would come before climate change
that it doesn't seem that productive. It sounds to me like scary
rhetoric to try to get funding, or to get people all excited about it."

Scientists will need at least a decade's more work before drawing any
definitive conclusions about population numbers, Rob Condon, a marine
scientist at Dauphin Island Sea Laboratory in Alabama who headed the
cycle paper, told LiveScience in a previous interview.

Haddock encourages anyone interested in jellyfish to submit sightings
to his group, JellyWatch.org, to help move the research along.
Gershwin,
meanwhile, worries that waiting may make it too late to stop the
invasion, if it is indeed happening.
"We're conducting this enormous global experiment, damaging the oceans, and the ocean is our life support system," she said.
"As crazy as it sounds, I think humanity needs a rethink," Gershwin
added.
"We need to really think about how important is that life support
system, how important is food from the ocean to us. Are we comfortable
polluting it and poisoning it and wiping it off the face of the Earth?
Is that the result we want for our future and our kids and our
grandkids?"